Method of reducing and elongating tubular blanks



1932- s. E. DIESCHER 1,870,209

METHOD OF REDUCING AND ELONGATING TUBULAR BLANKS FiledApx il 4. 1931 2Sheets-Sheet l WITHES$ :5 Il:\lVENTOR E 2 5M IE. I I 4 E Patented Aug.1932 UNITED STATES SAMUEL E. DIIEJSCHEB, OF PITTSBURGH, PENNSYLVANIAmn'rnon or annucme AND ELONGATING TUBULAR BLaNKs Application filed April4,

The invention relates to the manufacture of seamless tubing, the objectbeing to improve the method of manufacture thereof disclosed in myPatent No. 1,280,683.

Accordin to the method of manufacturing seamless tu es disclosed in mysaid patent, and as such method was practiced prior to -my. presentinvention, a tubular blank of metal is elongated and reduced in wallthickness by subjecting it while on a mandrel to the reducing action ofa pair of cross or equivalent helically-acting rolls, the peripheralflow of the metal as it is'reduced being controlled, being divertedlongitudinally of the blank, by the faces of grooved or equivalentdriven rolls acting upon the blank intermediate thepoints of contact ofthe reducing rolls with the blank. Lateral bulging of the blank beingreduced is prevented by'the surfaces of the grooved rolls which arespaced from the mandrel a distance equivalent to the wall thickness ofthe reduced-tube.

. In the operation of a tube-reducing mill such as shown in my saidpatent, and accord ing to the method therein explained, the forwardportions of reduced tubes, particularly long tubes, contract to such anextent while cooling that they grip the mandrels and tend to carry themforwardly at the rates of elongation and formation of the tubes, whichrates are in excess of the longitudinal movements of the m'andrelsproduced by the forwardly feeding action of the rolls. As a result ofthis, the reduced metal of the tubes adjacent to the rolls, which metalis in a heated and con sequently plastic condition,

frequently, when great reductions of wall .thicknesses are attempted,becomes upset in annular waves or bulges, thus completely destroying thetubes or rendering them unsuitable for uses where uniformity in theirdiameter is essential. Furthermore, regardless of whether the tubesbecome so distorted, the shrinkage and contraction of them upon themandrels makes it necessary to reel the tubes to such an extent thattheir internal diameters are sufiiciently enlarged to strip the tubesfrom the mandrels. Also, when tubes are not distorted in the manner justexplained, it is necessary to use longer mandrels 1931. Serial No.527,652.

than required for normal operation, because the shrinking of a tube upona mandrel causes the mandrel to be moved forwardly at a higher rate thanthe normal feeding rate of the rolls. These several factors result 65 inadditional labor and operating expenses, and subject the mandrels tosuch wear that frequent replacement of them becomes necessary. Inaddition to these prejudicial features of the method disclosed in saidpatent, it is necessary to provide a large number of different diameter,mandrels, the number depending upon the different internal diameters oftubing desired to be roduced, because the internal diameter 0 each tubeis fixedand determined by the diameter of the mandrel on which it isformed.

More specificallystated, the object of this invention is to improve themethod of manufacturing seamless tubes disclosed in my said patent tothe end that the formed tubing will have an internal diametersufliciently larger than the diameter of the mandrel that the tubingwill not shrink into binding contact withthe mandrel accompanied withthe above-explained prejudicial consequences, and that much greaterwallreductions and tube elongations'may be efiected; a'ndto the furtherends that a single size of mandrel may be used in the manufacture oftubing having different internal diameters, and that shorter mandrelsmay be used.

In the practice of my present invention-a tubular blank is reduced inwall thickness and elongated, in a manner generally similar to thatdisclosed in my said'patent, by subjecting theblank while on a mandrelto the reducing action of a pair of cross or equivalent helically-actingrolls, but in my improved method the tubular blank is permit-2 ted totake a cross-sectional form in which .it bulges laterally from thoseportions of the surface of the mandrel that lie between the oppositelydisposed points of engagement of thecross rolls with the blank. Thereducing pressure of the cross rolls on the blank causes the metal 'toflow from the pressure points, and, considered as to its peri heral andlongitudinal components,, such ow is predominantly peripheral, as iswell known.

ripheral flow of the metal is controlled (being diverted longitudinallyof the blank, that is,-converted into a flow having a largerlongitudinal component) by a pair of driven grooved or equivalent rolls,or guide disks,-

arranged between the cross rolls, the surfaces of which grooved rollsact upon the exterior of the blank at the portions thereof which havebeen caused to bulge laterally from the surface of the mandrel. At itspoint of reduction, the blankthus becomes substantially elliptical incross section with a larger interior circumference than thecircumference of the mandrel, the ellipticity, or bulging form of theblank, being much less, however, than it would be if the lateral bulgingwere not limited by the guide disks. As the elliptically-sha-ped blankor tube moves fortions of the cross rolls. In this way a trulycylindrical tube is formed of any desired wall thickness, dependingupon-the positioning of the reducing rolls, and having an internaldiameter larger than the diameter of the mandrel, and having an externaldiameter controlled by the positioning of). the

guide disks, and which may, as shown in the drawings, be substantiallyless than the external' diameter of the blank.-

The invention will be further explained with reference to theaccompanying drawings which illustrate, somewhat diagrammatically, amill operating upon a tubular blank. In the drawings, Fig. lis a faceview of the mill looking in the direction of feed of a blank through it,the mandrel and blank being shown in transverse section at the throat ofthe pass; Fig. 2 a vertical central sectional view through the milltaken on the line II- II, Fig. 1; Fig. 3 a horizontal sectional Viewtaken on the line III-III, Fig. 2; and Fig. 4 a sectionalview through amandrel and reduced tube, the plane of view being indicated by the lineIV-IV, Fig. 3.

The mill illustrated in the drawings comprises a pair of oppositelydisposed cross rolls 1 having their axes inclined to each other and tothe line of feed of a blank between them. Although these rolls are shownas of general barrel shape form, they may be of mushroom or of any othersuitable shape. Disposed between the cross rolls, and on opposite sidesof the pass between them, there.

are a pair of adjustably-mounted grooved guide rolls or disks 2arranged'onhorizontal axes and adapted to be driven-in any suitablemanner through wabblers 3. .In the-pass formed between these two pairsof rolls there is shown a cylindrical mandrel 5 arranged in a tubularblank 6 undergoing elongation formed on them.-

and reduction in wall thickness by the combined actions of the rolls.

The cross rolls 1 reduce the wall thickness of the tubular blank in theusual manner, causing the metal thereof to flow peripherally and to someextent longitudinally, and they cause the blank to bulge laterally fromthe surface of the mandrel and in engage ment with the surfaces of thedriven grooved rolls or disks 2 which prevent its further lateralbulging, and accordingly determine the ultimate circumference of thereduced tube, and which rolls or disks divert longitudinally of. theblank the peripheral flow of the metal, and exert a pull on the blank inthe direction of its longitudinal movement. The lateral bulging of theblank from the mandrelis indicated by the spaces 8 in Figs. 1 and2. Tobring the reduced tubular blank from its general elliptical formshown inFig. 1 to its truly cylindrical form shown in Fig. 4, the cross rolls 1are .each provided with surfaces 7 which flare outwardly from the neckof the pass which they form, and hence gradually reduce the major andincrease the minor axis of theelliptical blank until they merge into thediameter of a cylindrical tube. This action of the flaring surfaces ofthe cross rolls may be varied by suitable-adjustment of the axes of therolls, as well as by the initial taper of the surfaces.

The grooved guide rolls 2 are driven to rotate in the direction ofmovement of a blank passing between them, and at such angular velocityas to greatly reduce or to eliminate transverse friction between theirsurfaces and that of the. rotating blank upon which 'eral speed of theguide rolls, with the reducing rolls set at the feed angle shown in thedrawings, or at any desired angle within the range of customary practicefor cross'. rolling mills, will, of course, according to this formula,be greater than the peripheral speed of the blank and, therefore, of thereducing rolls. and substantiallyin excess of the speed of thelongitudinalmovement of the blank. -By thus overcoming transversefriction between the surfaces of grooved rolls and the rotating blank,wear on thegrooved rolls is reducedtofa minimum, and the tendency of thegrooved rolls to tear or otherwise prejudicially act upon the metal iseliminated.

In the practice of this invention in the manufacture of seamless tubingof different diameters by theme of a single mandrel,the

' grooved guide rolls or disks are so adjusted,

vertically in the illustrative embodiment of the invention, to or fromeach other that the average of the minimum distance between theirworking surfaces and the minimum distance between the cross rolls at theneck of the pass is approximately the outer diameter of the desiredtube. The maximum distance atwhich the grooved rolls may be spaced fromthe mandrel is that at which the material of the blank will tolerate,without in jury, repeated bending'in its changes from its originalcylindrical form to its maximum elliptical and then to its finalcylindrical form. 4

The invention may be practiced on either heated or cold cylindricalblanks. lVith either, the cross rolls act upon the metal between themand the mandrel to effect a reduction in wall thickness-of a blank,while the grooved guide rolls, contacting with the exterior surfaces ofa blankwhich is unsupported by the mandrel, serve to determine theultimate diameter of the reduced tube and aid in feeding the blankthrough the pass. While the method is applicable to reduction of bothhot and cold blanks, it. is especially advantageous in the reduction ofhot blanks in that it eliminates the possibility I proved method, in thepractice of it I have manufacture seamless tubing from wrought of areduced heated blank shrinking upon the mandrel with the attendingdifliculties previously explained.

As illustrative of the advantage in my im- I claim as my invention: i 1.The method of reducing the wall thickness and elongating a tubular metalblank, which comprises cross-rolling the blank on a mandrel betweenhelically acting reducing rolls on opposite sides of the blank to reducethe wall thickness of the blank and cause it to bulge laterally awayfrom the mandrelbetween the rolls and to feed the blank longitudinally;and diverting longitudinally the peripheral flow of the metal, andlimiting the bulging of the blank to determine the di ameter of theformed tube, and pulling the blank forward in the pass, by surfacesbearing on the blank between the reducing rolls andmoving in thedirection of the longitudinal movement of the blank ata speed greaterthan the speed of longitudinal move- 7 ment of the blank; therebyforming atube of greater. internal circumference than the mandrel.

2. The method of reducing the wall thickness andelongating a tubularmetal blank, which comprises cross-rolling the blank on a mandrelbetween helically acting reducing rolls on opposite sides of the blankto reduce the wall thickness of the blank and cause it to bulgelaterally away from the mandrel between the rolls and to feed the blanklongitudinally; and diverting longitudinally the peripheral flow of themetal, and limiting the bulging of the blank to determine the diameterof the formed tube, and pulling the blank forward in the pass, by guidedisks bearing on the blank between the reducing rolls and rotating tomove in the direction I of the longitudinal movement of the blank at aspeed greater than the speed of longi- 'tudinal movement of the blank;and promandrel between helically-acting reducing rolls on opposite sidesof the blank to reduce the wall thickness of the blank and cause it tobulge laterally away from the mandrel between the rolls and to feed theblank longitudinally; and diverting longitudinally the peripheral flowof the metal, and limiting the bulging of the blank, and pulling theblank forward in the pass, by surfaces bearing on the blank between thereducing rolls and moving in the direction of the longitudinal movementof the blank at a speed greater than the speed of longitudinal movementof the blank; and determining the wall thickness of the tube by thespacing of the reducing rolls and independently thereof the diameter ofthe tube by the spacing of the bearing surfaces.

.4. The method of reducing wall thickness and elongating tubular metalblanks, which comprises cross-rolling a blank on a mandrel betweenreducing rolls acting in conjunction with rotating guide disks, thereducing rolls reducing the Wall thickness of the blank and causing itto take a bulging form between the cross-rolling rolls, and the guidedisks divert- 1ng longitudinally the peripheral flow of the metal andlimiting the lateral bulging of the blank and pulling the blank forward,and determining the diameter of the formed tube independently of thesetting of the reducing rolls by adjusting the guide disks toward andfrom the mandrel.

In testimony whereof, I sign my name.

' SAMUEL E. DIESCHER.

